This paper presents the design and implementation of intraGrid, an experimental grid based on the Globus Toolkit™ and deployed on the IBM intranet. The architecture and the main components of intraGrid are described. Then, the major technical challenges and their solutions are reviewed, including software packaging and distribution, the interface for administrative tasks, and the design and implementation of the three major services: information services, management services, and job submission services. The paper also describes the extensions and modifications to intraGrid that were required to create the ISD grid, a grid that is used for joint projects with customers and thus requires access by external users. The paper reviews the use of intraGrid by various teams of IBM researchers to date and outlines the plans for future applications. The work in progress to migrate the intraGrid to an OGSA-based (Open Grid Services Architecture-based) grid is also described.